com.cc.nettytest.proxy.encoder.CCLengthFieldPrepender.java Source code

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Here is the source code for com.cc.nettytest.proxy.encoder.CCLengthFieldPrepender.java

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package com.cc.nettytest.proxy.encoder;

/*
* Copyright 2012 The Netty Project
*
* The Netty Project licenses this file to you under the Apache License,
* version 2.0 (the "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at:
*
*   http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
* License for the specific language governing permissions and limitations
* under the License.
*
* MODIFIED TO CHANGE ENDIANNESS for ClareControls
*/

import io.netty.buffer.ByteBuf;
import io.netty.buffer.ByteBufUtil;
import io.netty.channel.ChannelHandler.Sharable;
import io.netty.channel.ChannelHandlerContext;
import io.netty.handler.codec.MessageToByteEncoder;

import java.nio.ByteOrder;

/**
* An encoder that prepends the length of the message.  The length value is
* prepended as a binary form.  It is encoded in either big endian or little
* endian depending on the default {@link ByteOrder} of the current
* {@link ByteBufFactory}.
* <p>
* For example, <tt>{@link LengthFieldPrepender}(2)</tt> will encode the
* following 12-bytes string:
* <pre>
* +----------------+
* | "HELLO, WORLD" |
* +----------------+
* </pre>
* into the following:
* <pre>
* +--------+----------------+
* + 0x000C | "HELLO, WORLD" |
* +--------+----------------+
* </pre>
* If you turned on the {@code lengthIncludesLengthFieldLength} flag in the
* constructor, the encoded data would look like the following
* (12 (original data) + 2 (prepended data) = 14 (0xE)):
* <pre>
* +--------+----------------+
* + 0x000E | "HELLO, WORLD" |
* +--------+----------------+
* </pre>
*/
@Sharable
public class CCLengthFieldPrepender extends MessageToByteEncoder<ByteBuf> {

    private final int lengthFieldLength;
    private final boolean lengthIncludesLengthFieldLength;

    /**
     * Creates a new instance.
     *
     * @param lengthFieldLength the length of the prepended length field.
     *                          Only 1, 2, 3, 4, and 8 are allowed.
     *
     * @throws IllegalArgumentException
     *         if {@code lengthFieldLength} is not 1, 2, 3, 4, or 8
     */
    public CCLengthFieldPrepender(int lengthFieldLength) {
        this(lengthFieldLength, false);
    }

    /**
     * Creates a new instance.
     *
     * @param lengthFieldLength the length of the prepended length field.
     *                          Only 1, 2, 3, 4, and 8 are allowed.
     * @param lengthIncludesLengthFieldLength
     *                          if {@code true}, the length of the prepended
     *                          length field is added to the value of the
     *                          prepended length field.
     *
     * @throws IllegalArgumentException
     *         if {@code lengthFieldLength} is not 1, 2, 3, 4, or 8
     */
    public CCLengthFieldPrepender(int lengthFieldLength, boolean lengthIncludesLengthFieldLength) {
        super(ByteBuf.class);

        if (lengthFieldLength != 1 && lengthFieldLength != 2 && lengthFieldLength != 3 && lengthFieldLength != 4
                && lengthFieldLength != 8) {
            throw new IllegalArgumentException(
                    "lengthFieldLength must be either 1, 2, 3, 4, or 8: " + lengthFieldLength);
        }

        this.lengthFieldLength = lengthFieldLength;
        this.lengthIncludesLengthFieldLength = lengthIncludesLengthFieldLength;
    }

    @Override
    public void encode(ChannelHandlerContext ctx, ByteBuf msg, ByteBuf out) throws Exception {

        int length = lengthIncludesLengthFieldLength ? msg.readableBytes() + lengthFieldLength
                : msg.readableBytes();
        switch (lengthFieldLength) {
        case 1:
            if (length >= 256) {
                throw new IllegalArgumentException("length does not fit into a byte: " + length);
            }
            out.writeByte((byte) length);
            break;
        case 2:
            if (length >= 65536) {
                throw new IllegalArgumentException("length does not fit into a short integer: " + length);
            }
            out.writeShort((short) length);
            break;
        case 3:
            if (length >= 16777216) {
                throw new IllegalArgumentException("length does not fit into a medium integer: " + length);
            }
            out.writeMedium(length);
            break;
        case 4:
            out.writeInt(ByteBufUtil.swapInt((int) length)); //SWAP FOR UIMANAGER
            break;
        case 8:
            out.writeLong(length);
            break;
        default:
            throw new Error("should not reach here");
        }

        out.writeBytes(msg, msg.readerIndex(), msg.readableBytes());
    }
}